Recently there has been a rapid growth in a new area of research known asWireless Health.1 By leveraging stateof-
the-art microelectronics and wireless technology, novel biosensing platforms can potentially be widely deployed
in various healthcare applications that involve long-term patient monitoring. This paper provides a summary on
the development and application of a specific type of biosensing platform known as wearable sensors.
Today's state-of-the-art medical vests and shirts for health status monitoring are inflexible and expensive. The high cost
and the lack of flexibility and integral-unity of the current vests are prohibiting factors for their use in first responder
applications. The vests also lack an in-built intelligence to accurately determine the health status of the person wearing
the vest. We present a hardware plus software solution for monitoring the health status of first responders in pressurized
and adversarial missions. The technology consists of two main components. The first component is a physiological vest
consisting of a suite of physiological sensors interfaced with energy management units designed to prolong the life of the
sensors. The sensors communicate wirelessly with a personal server consisting of a Decision Support Software (DSS),
which forms the second major component of our technology. The DSS (1) integrates the physiologic sensors readings for
global assessment of the individual's health status; (2) recommends medical Alerts and Actions based on the fusion of
the sensor readings; and (3) applies cognitive computation to personalize the medical vest to the specific physiologic and
motion characteristics of the individual wearing the vest, in the theater of the operation or during exercise.
KEYWORDS: Software frameworks, Digital signal processing, Unattended ground sensors, Analog electronics, Telecommunications, Signal processing, Interfaces, Sensors, Software development, Global Positioning System
A low-power hardware platform and a software framework to support distributed wireless sensing for unattended ground sensor (UGS) applications has been developed. This platform provides a comprehensive set of hardware capabilities needed to meet the sensing, processing, and communication requirements for UGS, including a 16-channel analog interface, a processor dedicated to managing real-time requirements, dual wireless interfaces, and a low-power system bus to enable system modularity. An open software framework based on the Linux kernel is hosted on the main system processor. This framework incorporates the tools for effectively utilizing the capabilities of the hardware platform and rapidly developing applications in a networked, embedded environment.
KEYWORDS: Digital signal processing, Unattended ground sensors, Analog electronics, Software frameworks, Sensors, Power supplies, Embedded systems, Clocks, Signal processing, Control systems
A system architecture, and a hardware implementation leveraging the architecture, has been developed for energy-aware, networked, embedded systems designed for use in tactical unattended ground sensor (UGS) applications. This modular system architecture is designed around a flexible bus design that meets the needs for low-power embedded systems, incorporating support for 32-bit inter-module data transfers, module synchronization, power control, and power distribution. A Linux-based software framework operating on the main system processor has been developed to provide application developers with the ability to easily leverage the hardware functionality of the system. The low-power design methods employed in the system design are discussed along with a system implementation using these methods.
In the development of distributed security sensor networks a large variety of prototype systems have been implemented and tested. However these systems tend to be developer specific and require substantial overhead in demonstrating more than one application. To bridge the gap between embedded, networked systems and desktop simulation environments, systems are necessary which are easily deployable and allow extended operation of distributed sensor networks, while allowing the flexibility to quickly test and evaluate a variety of operational algorithms. To enable fast optimization by leveraging the widest development community, open standards for such a portable development system are desired. An open development system allows individual developers and small groups to focus on and optimize specific aspects of a distributed sensor network within realistic deployment constraints, prior to complete integration and deployment of a system within a specific application. By providing an embedded sensor and processing platform with integrated wired and wireless networking, a modular software suite separating access and control of individual processes, and open APIs, algorithm development and software optimization can be greatly accelerated and more robustly tested. To meet the unique needs of distributed sensor network applications, additional separation must be provided between the access to various subsystems, for example real-time embedded control versus tasks with less stringent timing requirements. An open platform that separates these requirements allows developers to accelerate testing and development of applications by focusing on individual components of the distributed sensor system, such as target tracking or low power networking. The WINS NG 2.0 developer's platform, provided by Sensoria Corporation for the DARPA/ITO Sensor Information Technology (SensIT) program, provides one example of such a system. This systems bridge the gap between dedicated desktop development environments and embedded application-specif
Wireless Integrated Network Systems (WINS) provide distributed network and Internet access to sensors, controls, and processors that are deeply embedded in equipment, facilities, and the environment. The WINS network is a new monitoring and control capability for applications in transportation, manufacturing, health care, environmental monitoring, and safety and security. WINS combine microsensor technology, low power signal processing, low power computation, and low power, low cost wireless networking capability in a compact system. WINS networks will provide sensing, local control, and embedded intelligent systems in structures, materials, and environments. This paper describes the WINS architecture and WINS technology components including sensor interface and WINS event recognition systems.
Tony Tang, Roman Gutierrez, Jaroslava Z. Wilcox, Christopher Stell, Vatche Vorperian, Mike Dickerson, Barry Goldstein, Joseph Savino, Wen Li, Robert Calvet, Indrani Charkaborty, Randall Bartman, William Kaiser
This paper reports on the design, modeling, fabrication, and characterization of a novel silicon bulk micromachined vibratory rate gyroscope and a 3-axes rotation sensing system using this new type of microgyroscopes designed for microspacecraft applications. The new microgyroscope consists of a silicon four leaf clover structure with a post attached to the center. The whole structure is suspended by four thin silicon cantilevers. This device is electrostatically actuated and detects Coriolis induced motions of the leaves capacitively. A prototype of this microgyroscope has a rotation responsivity (scale factor) of 10.4 mV/deg/sec with scale factor nonlinearity of less than 1%, and a minimum detectable noise equivalent rotation rate of 90 deg/hr, at an integration time of 1 second. The bias stability of this microgyroscope is better than 29 deg/hr. The performance of this microgyroscope is limited by the electronic circuit noise and drift. Planned improvements in the fabrication and assembly of the microgyroscope will allow the use of Q-factor amplification to increase the sensitivity of the device by at least two to three orders of magnitude. This new vibratory microgyroscope offers potential advantages of almost unlimited operational life, high performance, extremely compact size, low power operation, and low cost for inertial navigation and altitude control.
The next generation of navigation sensors, which includes microaccelerometers and microgyroscopes, presents high challenges in developing sensitive interface circuits. The shrinking sensor dimensions lead to small output signals that must be processed by the interface electronics. This paper presents a novel interface circuit that can be applied to both fully-differential capacitive and piezoresistive sensors. An equivalent Blumlein Bridge circuit is implemented on CMOS using a novel feedback loop that balances the signals applied to the transducer electrodes. Charge injection is drastically reduced by a double sampling method and a novel adaptive feedback loop that incorporates a compensation switch. The charge injection is reduced to a level below the thermal noise of the opamp. In addition, the feedback loop that is used for reducing the charge injection eliminates supply drift errors. Resolution and stability levels of 10-8 with a supply variation of 10% are achieved.
Pyroelectric detectors based on PbTiO3 (PTO) and Pb1-xCaxTiO3 (PCTx) were fabricated and evaluated on thin silicon micro electrical-mechanical structures (MEMS) utilizing a new sol-gel technique. The sol-gel approach allows arbitrary Pb:Ca ratio, and is fully compatible with existing CMOS processes. The novel precursor chemistry developed in our laboratory is not moisture sensitive, and has a shelf-life of many months. Layers of PTO precursor were spin-coated onto 4 micrometers thick silicon membrane structures. Heat treatment at 700 degree(s)C yielded crack-free films approximately 0.3 micrometers thick. Contacts to the top of the pyroelectric film and to the silicon membrane were made by thermal evaporation of aluminum. The reduced thermal capacitance and improved thermal isolation offered by the MEMS membrane structure have significantly improved the performance of our device over typical bulk single crystal or ceramic devices. Pyroelectric responsivity of 2.5 volt/watt was measured at (lambda) equals 10.6 micrometers for a first generation simple membrane structure without poling or electrical bias. SPICE analysis of a distributed thermal circuit model indicates the potential for two orders of magnitude improvement in device sensitivity for optimized membrane structures currently under construction. These results also indicate that a fully integrated high-performance room temperature imaging array for use in the far IR can be realized at low cost.
Microgyroscope applications are increasing in many fields, creating a need to develop low cost, compact gyroscopes. A full understanding of the operation principles and limitations of a rate gyroscope are essential in creating a small and low-cost device. Currently, there is no simulation tool available that can simulate both the electronic and nonelectronic components of a complete device. The work described in this paper presents a method to simulate a complete comb-drive rate microgyroscope using the SPICE electronic simulation tool. The simulation method given here can be generalized to a wide range of MEMS devices. An equivalent circuit was developed and simulated using SPICE. Results of the frequency response, and transient analysis are given. The results obtained reproduce the reported device operation. A set of important new findings are revealed from the analysis using this new tool. Using the transient analysis, for example, we can see that the requirement of a large quality factor of the sensor causes a very slow (open-loop) response and that a closed-loop operation is essential in this device. In addition, the nonideal factors are described and are analyzed using SPICE.
A novel micromachined electrostatically controlled deformable mirror has been fabricated and characterized. This device combines the fields of microinstruments, adaptive optics and controls to form a silicon-based mirror assembly that is relatively simple to process, inexpensive, lightweight, and integrable with drive and sensing electronics. Electrostatic control of a thin membrane mirror is demonstrated with low voltage actuation and without the need for complex construction of PZT or other translator-type arrays. In addition, the low- stress Si-rich SixNy film used as the deformable membrane mirror is thermally matched to the silicon supporting frame. Custom design of the mirror shape can be implemented by redesigning the electrode pattern on an insulating substrate separate from the thin film mirror. Test results from a pull-only circular mirror with a single actuator are presented as a proof of concept for low voltage actuation of a low-stress SixNy flexible membrane. The SixNy which forms the membrane is under tensile stress. This tensile stress increase the voltage required for deflection of the membrane, but insures a linear relationship between the center deflection of the mirror and the applied pressure. This should significantly simplify the controls algorithm required for closed-loop operation of this device.
An important new approach for vehicle guidance and control is based on the use of compact, low-mass, low-cost sensors integrated with the vehicle structure. Many advantages of this approach lead to new capabilities. However, the development of compact guidance and control sensors leads to a variety of fundamental physical problems associated with sensor sensitivity and noise. For example, as sensor size is reduced, it becomes necessary to improve the sensitivity of the sensor signal detection mechanism. These challenges to sensor development will be described. Recent developments at JPL, based on new position sensor principles such as electron tunneling, have produced a series of novel, ultra-high sensitivity micro-sensors and micro-instruments. Included among the applications demonstrated, are a high sensitivity micro-accelerometer and micro-seismometer. In this paper, the fundamental limits of conventional position sensors will be discussed and a new position sensor for advanced accelerometers will be described.
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